Hurricane IGOR (Text)

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HURRICANE IGOR DISCUSSION NUMBER 39
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
500 PM AST FRI SEP 17 2010
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING IGOR
EARLY THIS AFTERNOON MEASURED A MINIMUM PRESSURE OF 946 MB. THE
HURRICANE HUNTER ALSO MEASURED MAXIMUM FLIGHT-LEVEL AND SFMR WINDS
OF 102 AND 79 KT...RESPECTIVELY. THE INITIAL INTENSITY IS LOWERED
TO 90 KT BASED UPON THE AIRCRAFT OBSERVATIONS. DATA FROM THE PLANE
ALSO INDICATED A RATHER BROAD WIND FIELD...WITH THE PRESENCE OF A
DOUBLE WIND MAXIMA. SINCE THE PLANE DEPARTED...THE CLOUD PATTERN OF
IGOR HAS INCREASED IN ORGANIZATION...WITH COLDER CLOUD TOPS
DEVELOPING WITHIN THE INNER CORE AND THE EYE BECOMING VISIBLE
AGAIN. INNER CORE DYNAMICS NOTWITHSTANDING...THERE APPEARS TO BE A
FINAL WINDOW OF OPPORTUNITY FOR RE-INTENSIFICATION DURING THE NEXT
DAY OR SO AS IGOR REMAINS IN A LIGHT SHEAR ENVIRONMENT AND MOVES
OVER WARM WATERS. AFTER ABOUT 36 HOURS...A GRADUAL INCREASE IN
SOUTHERLY AND SOUTHWESTERLY SHEAR AND COOLER WATERS ALONG THE
FORECAST TRACK SHOULD PROMOTE A WEAKENING OF IGOR. THE OFFICIAL
INTENSITY FORECAST HAS BEEN ADJUSTED DOWNWARD A BIT IN THE SHORT
TERM BASED UPON CURRENT TRENDS BUT IS NEARLY THE SAME LATER IN THE
PERIOD. IN AGREEMENT WITH THE GUIDANCE...IGOR IS FORECAST TO BECOME
A LARGE AND STRONG EXTRATROPICAL CYCLONE OVER THE FAR NORTH
ATLANTIC BEYOND 96 HOURS.
IGOR APPEARS TO BE ON TRACK...AND THE INITIAL MOTION ESTIMATE IS
305/09. THE TRACK FORECAST PHILOSOPHY HAS NOT CHANGED. IGOR
SHOULD BE STEERED NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD AROUND
THE WESTERN SIDE OF A SUBTROPICAL RIDGE DURING THE NEXT 36 HOURS.
AFTER THAT...A VIGOROUS SHORTWAVE TROUGH MOVING ACROSS THE
NORTHEASTERN U.S. SHOULD GRADUALLY TURN THE HURRICANE NORTHWARD IN
THE VICINITY OF BERMUDA...AND THEN NORTHEASTWARD WITH A SUBSTANTIAL
INCREASE IN FORWARD SPEED. THE OFFICIAL NHC TRACK FORECAST IS VERY
CLOSE TO THE PREVIOUS ONE AND REMAINS CLOSE TO THE MULTI-MODEL
CONSENSUS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.
THE WIND RADII HAVE BEEN EXPANDED BASED UPON DATA FROM THE
RECONNAISSANCE AIRCRAFT AND AN EARLIER ASCAT OVERPASS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 17/2100Z 23.7N 61.1W 90 KT
12HR VT 18/0600Z 24.8N 62.4W 95 KT
24HR VT 18/1800Z 26.2N 64.0W 100 KT
36HR VT 19/0600Z 27.9N 64.9W 95 KT
48HR VT 19/1800Z 30.0N 65.1W 90 KT
72HR VT 20/1800Z 35.5N 62.0W 85 KT
96HR VT 21/1800Z 43.5N 52.5W 75 KT...POST-TROP/EXTRATROP
120HR VT 22/1800Z 52.0N 44.0W 65 KT...POST-TROP/EXTRATROP
$$
FORECASTER KIMBERLAIN
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